Diesel engines compress air-fuel mixtures to initiate combustion in engine cylinders. Glow plugs may be used during starting of a cold diesel to assist engine starting when compression of the air-fuel mixture may be insufficient to produce automatic ignition of an air-fuel mixture. The glow plugs may be positioned in a combustion chamber to elevate the temperature of a portion of an in cylinder air-fuel mixture so that the air-fuel mixture may ignite when compressed. Once the engine is started the glow plugs may be turned off or operated at a low current for a predetermined amount of time to conserve energy and extend glow plug life. However, it may not be desirable to deactivate glow plugs after an engine start simply because the engine is started. Further, it may be desirable during some engine operating conditions to control glow plugs responsive to conditions other than an indication that an engine is started.
The inventors herein have recognized the above-mentioned disadvantages and have developed an engine operating method, comprising: performing combustion in a cylinder of an engine; and retarding combustion phasing in the cylinder and increasing current supplied to a glow plug in the cylinder in response to a temperature of a catalyst and a temperature of the engine.
By selectively operating glow plugs after engine start during different engine operating conditions, engine hydrocarbons may be reduced while engine combustion stability is increased. Further, engine heat output can be increased when glow plugs are activated to improve catalyst light off or regeneration of emissions control devices. For example, if an engine enters low load conditions where temperature of a catalyst coupled to an exhaust system of the engine may be reduced, glow plugs can be activated and combustion phasing retarded so that catalyst efficiency may be maintained or improved. Further, in systems where a motor is coupled to the engine, the motor may be adjusted to compensate or account for the response time of the glow plug so that engine emissions can be controlled during the time it takes for the glow plug to reach a desired operating temperature. In this way, glow plugs may be selectively operated so as to improve engine operation and emissions.
The present description may provide several advantages. In particular, the approach may improve engine operation during conditions where emissions control devices coupled to the engine are operating with less than desired efficiency. In addition, the approach provides compensation for glow plug heating response time. Further, the approach may reduce engine emissions after the engine reaches warmed up operating conditions by allowing the engine to retard combustion phasing while continuing to provide stable combustion.
The above advantages and other advantages, and features of the present description will be readily apparent from the following Detailed Description when taken alone or in connection with the accompanying drawings.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.